The present invention relates to a microtome drive having a drive shaft for movement of the object carriage, and more particularly to a microtome drive wherein the drive shaft carries a hand wheel for manual drive and a V belt pulley for motor drive and wherein coupling means are provided between the hand wheel and the V belt pulley.
In known microtomes, the movement and guidance of the preparation is effected by a drive shaft located on the microtome and rotated either by a hand wheel or by an electromotor. A disadvantage of these instruments consists of the fact that, with the drive motor engaged, the hand wheel also rotates, so that the protruding manual handle represents a significant risk of accident. The risk of accident is further enhanced at that moment when the motor drive is already running and the coupling between the motor drive and the drive shaft or the hand wheel is effected at the hand wheel or in its immediate vicinity, since the hand wheel is thereby abruptly set into a rotating motion, in part while the shifting operation is still in progress. Furthermore, with the instrument at rest, the type of drive engaged is not apparent, i.e., it cannot be visually ascertained whether the motor or the manual drive is engaged.
In a microtome proposed very recently, these disadvantages are eliminated. For this purpose, in order to control the type of drive in this device, two push rods supported in bearings parallel to the drive shaft are provided in a bushing mounted fixedly on the drive shaft. These push rods are each exposed to the action of a compression spring and are capable of alternating actuation, whereby on the one hand a follower is uncoupled from the hand wheel which is then not moved when the microtome is motor driven, and on the other hand, the follower engages in a recess in the hand wheel, when the microtome is to be operated by hand. This microtome drive requires a relatively large number of individual parts and is thus expensive.
Furthermore, in this instrument the weight equalization provided to compensate for the mass of the object carriage moving in the vertical direction must rest on the drive shaft.